The invention relates generally to nondestructive methods for determining the integrity of components and structures. More particularly, the invention is a method and system for nondestructive test method qualification and probability of detection determination, for establishing and maintaining nondestructive testing proficiency of inspectors, for periodically presenting flaw signals to inspectors during routine inspections, and for ensuring sufficient scan coverage for detection of material defects in a test piece. The invention finds use in general nondestructive testing as well as where eddy current and ultrasound methods are used to detect the presence of flaws in components and structures.
Nondestructive testing (NDT) is used in many industries to detect the presence of flaws so that the integrity of components and structures may be determined. NDT involves using various test methods, such as eddy current and ultrasonics. Applications include military and civilian aircraft, fossil and nuclear electrical power generation equipment, petrochemical plants, etc. There are several needs within the NDT environment that, if satisfied, would significantly reduce inspection costs and improve the reliability and quality of inspections.
NDT method qualification and probability of detection (POD) determination is one area of need. Demonstration of the capability and reliability of new NDT techniques must often be done in a short period of time and at minimal cost. The present approach is to perform a POD study. These studies involve producing many test specimens with realistic flaws, training multiple NDT technicians, and conducting blind tests. Fabrication of the flawed specimens is very expensive and time consuming. As a result, a POD study is usually performed only for the most critical applications. A system and method to reduce costs and time required to implement POD studies is needed.
NDT inspectors must be trained to ensure proficiency in new and existing NDT procedures. Training is also required periodically in order to maintain proficiency of the inspectors through practice. Although specimens with realistic flaws are needed for training, they are often not available. Video-based training courses are available, but they do not provide xe2x80x9chands-onxe2x80x9d experience with real flaws. Therefore, better training methods are another area of need.
Monitoring existing inspections when flaws are infrequent presents another area of need. In some routine inspections, flaws are encountered very infrequently, sometimes less than once per year. Inspectors may become conditioned to not expecting flaws, resulting in a loss of proficiency. A method is needed to periodically present simulated flaws to inspectors during routine inspections.
Ensuring that a thorough scan is conducted over an entire test piece in another area of need. Some inspections are performed by hand scanning, and the scanning coverage of the appropriate area is dependent on the skill and attention of the operator. A method is needed to monitor scan position so that proper coverage is obtained.
The present invention provides for a system and method that satisfies the needs for reducing costs and time required to implement POD studies, providing improved realistic training methods, presenting simulated flaws to inspectors during routine inspections, and for monitoring scan position to ensure proper coverage of test pieces. This invention performs the functions of an NDT inspection simulator analogous to flight simulators used to train aircraft pilots. The operations of the NDT simulator are transparent to the inspector using the system when realistic, virtual flaw signals are presented at preprogrammed locations on the actual test piece. The virtual flaw signals may be premeasured or generated from a model. This method of presenting virtual flaws provides the equivalent of real flaws to an inspector without the requirement for having actual flaws in a test piece. The inspector may use the same probes and instrumentation of a conventional NDT instrument that are normally used in the inspection process. The simulator may be connected between the probe and NDT instrument so that flaw responses will be injected into the instrument, and the operator may view a response on the actual NDT instrument display. The probe and instrument may remain xe2x80x9clivexe2x80x9d, so that the interaction between the probe and the test piece remain active as well. The simulator may track the probe position so that responses from flaws can be injected at a selected location on the test piece.
The present invention enables POD tests to be accomplished without the need for manufacturing a large number of actually flawed test pieces. A training mode may be implemented in which the inspector receives instructions from the system and can practice with the equivalent of actual flawed test pieces. The system may be used with routine inspections to inject artificial flaw signals to keep inspectors alert, and may be used to monitor probe position in manual test scans to ensure proper coverage.
In another embodiment of the present invention, instead of injecting virtual flaws into a test instrument, the present invention may accept an output signal from an NDT test instrument, add virtual flaws to this signal within the system, and display the results on a computer monitor. This embodiment provides a virtual instrument for an inspector, who may view the computer monitor instead of the test instrument for conducting nondestructive tests.
An embodiment of the present is a method for nondestructive testing with flaw simulation, comprising the steps for storing a geometry of a test piece and a positional map of virtual flaw signals for the test piece in a control computer, causing a nondestructive testing probe to scan a test piece by movement of the probe over the test piece by an inspector, tracking nondestructive testing probe positions with respect to the test piece and sending probe position signals to the control computer, processing nondestructive testing probe output signals and displaying the processed signals to the inspector, injecting virtual flaw signals into the processed probe output signals based on the probe positions, the stored test piece geometry and the stored positional map for determining virtual flaw response signals, and displaying the virtual flaw response signals to the inspector. The steps for processing probe output signals and injecting virtual flaw signals may comprise the steps for sending excitation signals to the probe from conventional nondestructive test instrumentation through a virtual flaw signal injection circuit, receiving the probe output signals by a virtual flaw signal injection circuit, computing virtual flaw signals by the control computer based on the probe positions, the stored geometry of the test piece and the stored positional map of virtual flaw signals for the test piece, combining the probe output signals and the virtual flaw signals from the control computer by the virtual flaw signal injection circuit for determining the virtual flaw response signals, and sending the virtual flaw response signals from the virtual flaw signal injection circuit to the conventional nondestructive test instrumentation for displaying the virtual flaw response signals to the inspector by the conventional nondestructive test instrumentation. The method may further comprise sensing nondestructive testing probe liftoff from the test piece, sending probe liftoff signals to the control computer, and using the probe liftoff signals for computing virtual flaw signals. The steps for processing probe output signals and injecting virtual flaw signals may comprise the steps for sending excitation signals to the probe and receiving the probe output signals by conventional nondestructive test instrumentation, receiving output signals from the conventional nondestructive test instrumentation by the control computer, computing virtual flaw signals by the control computer based on the probe positions, the probe liftoff signals, the stored geometry of the test piece and the stored positional map of virtual flaw signals for the test piece, combining the conventional nondestructive test instrumentation output signals and the virtual flaw signals by the control computer for determining virtual flaw response signals, and sending the virtual flaw response signals from the control computer to a computer monitor for displaying the virtual flaw response signals to the inspector. The step for storing in a control computer may comprise the steps for reading and storing virtual flaw signals data, reading and storing the test piece geometry, generating one or more positional maps of virtual flaw signals for the test piece, and reading liftoff correction parameters. The step for computing virtual flaw signals by the control computer may comprise the steps for reading and storing the probe position signals, reading and storing the liftoff signals, reading and storing the positional map of virtual flaws, calculating virtual flaw signals using the probe position signals and the positional map, applying liftoff correction to the calculated virtual flaw signals, and sending the corrected virtual flaw signals to the virtual flaw signal injection circuit. The step for computing virtual flaw signals by the control computer may comprise the steps for reading and storing the output signals from the conventional nondestructive test instrumentation, reading and storing the probe position signals, reading and storing the liftoff signals, reading and storing the positional map of virtual flaws, calculating virtual flaw signals using the probe position signals and the positional map, applying liftoff correction to the calculated virtual flaw signals, and combining the corrected virtual flaw signals with the signals from the conventional nondestructive test instrumentation and sending the combined signals to the computer monitor. The nondestructive testing probe may be selected from the group consisting of an eddy current probe and an ultrasonic probe. A liftoff sensor may be selected from the group consisting of an eddy current sensor, a capacitive sensor and an optical sensor. The nondestructive testing probe may be selected from the group consisting of a single element probe for receiving excitation signals and transmitting test signals, a dual element probe for receiving excitation signals on one element and transmitting test signals from a second element, and a triple element probe for receiving excitation signals on one element and transmitting test signals differentially from the other two elements. The step for displaying the virtual flaw response signals may comprise the step for displaying the virtual flaw response signals and actual flaw response signals to the inspector. The method may further comprise the step for displaying virtual flaws to an inspector on a computer monitor connected to the control computer for instructional training purposes. The method may further comprise the step for deriving the positional map of virtual flaws from a model of conventional nondestructive test instrumentation responses. The method may further comprise the step for deriving the positional map of virtual flaws from actual premeasured flaw signals from conventional nondestructive test instrumentation. A computer-readable medium may contain instructions for controlling a computer system to implement the method above. A computer-readable medium may contain instructions for controlling a computer system to implement the step for computing virtual flaw signals disclosed above.
Another embodiment of the present invention is a system for nondestructive testing with flaw simulation that comprises means for storing a geometry of a test piece and a positional map of virtual flaw signals for the test piece in a control computer, means for causing a nondestructive testing probe to scan a test piece by movement of the probe over the test piece by an inspector, means for tracking nondestructive testing probe positions with respect to the test piece and sending probe position signals to the control computer, means for processing nondestructive testing probe output signals and displaying the processed signals to the inspector, means for injecting virtual flaw signals into the processed probe output signals based on the probe positions, the stored test piece geometry and the stored positional map for determining virtual flaw response signals, and means for displaying the virtual flaw response signals to the inspector. The means for processing probe output signals and injecting virtual flaw signals may comprise means for sending excitation signals to the probe from conventional nondestructive test instrumentation through a virtual flaw signal injection circuit, means for receiving the probe output signals by a virtual flaw signal injection circuit, means for computing virtual flaw signals by the control computer based on the probe positions, the stored geometry of the test piece and the stored positional map of virtual flaw signals for the test piece, means for combining the probe output signals and the virtual flaw signals from the control computer by the virtual flaw signal injection circuit for determining the virtual flaw response signals, and means for sending the virtual flaw response signals from the virtual flaw signal injection circuit to the conventional nondestructive test instrumentation for displaying the virtual flaw response signals to the inspector by the conventional nondestructive test instrumentation. The system may further comprise means for sensing nondestructive testing probe liftoff from the test piece, sending probe liftoff signals to the control computer, and using the probe liftoff signals for computing virtual flaw signals. The means for processing probe output signals and injecting virtual flaw signals may comprise means for sending excitation signals to the probe and receiving the probe output signals by conventional nondestructive test instrumentation, means for receiving output signals from the conventional nondestructive test instrumentation by the control computer, means for computing virtual flaw signals by the control computer based on the probe positions, the probe liftoff signals, the stored geometry of the test piece and the stored positional map of virtual flaw signals for the test piece, means for combining the conventional nondestructive test instrumentation output signals and the virtual flaw signals by the control computer for determining virtual flaw response signals, and means for sending the virtual flaw response signals from the control computer to a computer monitor for displaying the virtual flaw response signals to the inspector. The means for displaying the virtual flaw response signals may comprise displaying the virtual flaw response signals and an actual flaw response signals to the inspector. The system may further comprise displaying virtual flaws to an inspector on a computer monitor connected to the control computer for instructional training purposes.
In yet another embodiment of the present invention, a system for nondestructive testing with flaw simulation comprises conventional nondestructive testing instrumentation including a probe connected to a simulation means, means for tracking positions of the probe with respect to a test piece and providing a probe position tracking signal to the simulation means, means for sensing liftoff of the probe from the test piece and providing a probe liftoff signal to the simulation means, and the simulation means comprising a computer including means for monitoring the probe position tracking signal, means for monitoring the probe liftoff signal, means for storing virtual flaw signals that are a function of probe position, means for providing virtual flaw signals as a function of the probe position tracking signal and the probe liftoff signal for combining with nondestructive testing instrumentation probe signals, means for combining a signal from the conventional nondestructive testing instrumentation with a simulated virtual flaw signal from the simulation means, and means for displaying the combined signals to an inspector. The combining means may be a virtual flaw signal injection circuit for receiving virtual flaw signals and output signals from the probe, the virtual flaw injection circuit providing a combined signal to the conventional nondestructive testing instrumentation, and the displaying means may be the conventional nondestructive testing instrumentation for displaying actual and virtual flaws. The system may further comprise a display means connected to the simulation means for displaying simulated virtual flaw signals for instructional training purposes The combining means may be the simulation means for receiving an output signal from the conventional nondestructive testing instrumentation to be combined with the simulated virtual flaw signal, and the displaying means may be a computer monitor connected to the simulation means for displaying actual and virtual flaws. The conventional nondestructive testing instrumentation may be based on eddy current nondestructive testing methods. The conventional nondestructive testing instrumentation may based on ultrasonic nondestructive testing methods. The virtual flaw signals may be created from pre-measured signals from actual defects. The virtual flaw signals may be created from a mathematical model.
Although the present invention is described as an implementation of an NDT simulator for eddy current testing, it may be similarly applied to other NDT instrumentation methods, such as ultrasonics.